CVE-2025-66376
Cross-Site Scripting in Synacor Zimbra Collaboration Suite (ZCS). CISA confirmed attackers exploit it and added it to its Known Exploited Vulnerabilities catalog on 18 March 2026.
- Product
- Synacor Zimbra Collaboration Suite (ZCS)
- Added to CISA's catalog
- Federal fix-by date
- Ransomware
- No known use in ransomware campaigns
- Vendor advisories
- Sources
- CISA’s catalog, NVD entry
CISA’s description.
Synacor Zimbra Collaboration Suite (ZCS) contains a cross-site scripting vulnerability in the Classic UI where attackers could abuse Cascading Style Sheets (CSS) @import directives in email HTML.
More from Synacor this year.
- CVE-2026-73570 Zimbra Collaboration Suite (ZCS) OS Command Injection, added
- CVE-2025-48700 Cross-site Scripting, added
- CVE-2020-7796 (ZCS) Server-Side Request Forgery, added
- CVE-2025-68645 PHP Remote File Inclusion, added
Every flaw CISA confirmed exploited in the last 30 days is on the exploit watch. This is not security advice. Check the vendor’s advisory before acting. From CISA’s catalog of 4 November 2026.